DE. J. MURIE ON THE FORM AXD STEUCTITJE OF THE MANATEE. 177 



truly astonishing. Besides an axillary, however, I observed another trunk derivative of 

 the subcla^dan, and which may be representative of a thyroid axis, terminating in axillary 

 rete. In tracing continuations of the axillary rete I could distinguish circumflex 

 anterior and posterior bundles. The brachial rete diminishes as it reaches the elbow 

 and passing beneath the pronator radii teres, forms an ulnar rete. This keeps close to 

 the bone, under the forearm-muscles, and crosses obliquely to the proximal end of the 

 fifth digit. Here, besides muscular radicles, a bunch goes to the palmar aspect of the 

 wrist, and by intricate partition helps to constitute the palmar arch. The radial rete 

 appears less complicate, but unfortunately its manner of palmar division was not satis- 

 factorily made out. 



The multitudinous networks, nuchal, spinal, thoracic, and caudal, are sufficiently like 

 those of whales, and have been so frequently referred to by other authors, that I need 

 not dwell on them. As regards the intercostal plexuses, these do differ from those of 

 Cetacea, inasmuch as, instead of great contorted coils lying supei-ficial to the ribs, each 

 intercostal artery dips singly between the ribs, and in the space covered by the pleura 

 and muscles divides arborescently. With all due respect therefore to the accuracy 

 and acumen of our great leader. Professor Owen, I venture to predict the presence of 

 similar rete in the Dugong, where such arterial modification is denied. When unin- 

 jected the closely-packed vessels so simulate coarse muscular fibre as readily to deceive 

 one unless critically inspected. 



There is an abnormal rete, hitherto unrecorded, in continuance of the internal mam- 

 marj^ The latter vessel issues beneath the rectus abdominis, opposite the third costal 

 interspace, and proceeds upon the transversalis as a rete, which posteriorly anastomoses 

 with a returning epigastric series. Anteriorly the rami run outwards in parallel radii 

 like the plume of a pen. The abdominal surface of the posterior half of the diaphragm 

 is supplied Avith vessels and nerves arranged in a like fashion. I may advert to a retal 

 offshoot of the deep lumbo-caudal mass of vessels, which, for distinction's sake, may be 

 named either sacral, pelvic, or hypogastric rete. Derived from where the costal channels 

 strike within the chevron bones, it fonns a thin but wide sheet of arterial and venous 

 rami, which cover the sacro-coccygeus and parts beneath the urino-genital organs. 

 From it vesical and other supplies are given off", the most characteristic being a hypo- 

 gastric, obliterated beyond the fundus of the bladder, a uterine, and in the male sper- 

 matic plexus, with marked arteria dorsalis penis. 



Circumstances already mentioned prevented my observance of the giving off of the 

 abdominal aortic trunks or following the visceral distribution. The mesenteric vessels 

 appeared to split into primary, secondary, and tertiary arches without any striking 

 peculiarity in the vasia brevia, and the haemorrhoidal arterioles have inosculations with 

 the hypogastric rete. 



The veins of the face and head were not followed in detail. Branches, however, were 

 observed to return from the submaxillary region and outer side of the jaw ; these con- 



2d2 



